MADISON – The removal of Kirtland's warbler from the federal endangered species list on April 12 is another great conservation comeback story, and Wisconsin will continue its efforts to grow the tiny songbird's population.

The U.S. Fish & Wildlife Service announced earlier this week its plans to remove Kirtland's Warbler from the federal list of threatened and endangered species. The USFWS has determined that the species has clearly met recovery goals following years of intensive habitat management, mostly in lower Michigan where the core population is found.

Kirtland's warbler is a wood warbler that measures 5 1/2 inches long, weighs under a half ounce, and migrates to the Bahamas for the winter. The first nest was confirmed in Wisconsin in 2007. Photo credit: DNR

The species' numbers in Wisconsin don't yet meet the criteria to be removed from the state's endangered species list. However, Wisconsin continues to be active in conservation efforts for the species which began when it was first documented breeding here 10 years ago.

“This is a huge milestone for the overall recovery of this bird, and we will continue our work to increase the Wisconsin population,” says Drew Feldkirchner, who directs the Department of Natural Resources Natural Heritage Conservation Program. “Decades of commitment and hard work through public and private partnerships in Michigan have paid off, and we are also proud of the work our Wisconsin partners have done to increase our small but growing population.”

National recovery team leaders believe the Wisconsin population provides an important backstop to the core Michigan population and that newly established breeding areas on public land in northern Wisconsin will be important as hotter, drier conditions affect the warblers' food supply at breeding sites in Wisconsin and Michigan at lower latitudes.

Wisconsin's population has grown from only 11 Kirtland's warblers and three nests documented in 2007 to 53 birds and 20 total nests in 2017. Importantly, the population has grown and its range has expanded from Adams County to also include Marinette and Bayfield counties. The birds fledged a minimum of 49 and up to 63 young in 2017.

“Kirtland's are responding to a decade of conservation work from dedicated partners and the numbers of individuals and nests in Wisconsin continue to increase,” says Kim Grveles, the Department of Natural Resources conservation biologist who led Kirtland's warbler efforts in Wisconsin for the past decade.

“We're very encouraged by results of recent years and look forward to contributing more birds to the overall population in coming years,” she says.

The Kirtland's warbler was placed on the federal endangered species list about 40 years ago, when its Michigan population dropped to about 300 birds due to habitat loss and nest predation from brown-headed cowbirds.

Starting in the late 1990s, the protections and efforts made under the federal Endangered Species Act enabled the Kirtland's warbler to start expanding its breeding territory to Wisconsin, Michigan's Upper Peninsula and Ontario. The first nest was confirmed in Wisconsin in 2007.

To help increase Kirtland's warblers in Wisconsin, DNR, the U.S. Fish & Wildlife Service and other partners now conduct annual surveys in seven counties to listen and look for the birds, monitor nests in Adams County and Marinette County where breeding sites have been found, and set traps to keep cowbirds away from the warblers' nests.

The partners are also working to maintain and expand the mix of 5- to 20-year-old jack pine trees and barrens to provide quality habitat for Kirtland's warblers and other species, says Grveles.

In 2017, DNR planted a 125-acre jack pine stand near the Brule River in Douglas County. Also, Bayfield County Forest and Marinette County Forest continued their habitat management efforts that benefit Kirtland's warblers.

In addition to those county forests, DNR and U.S. Fish & Wildlife Service, other partners and collaborators include the University of Wisconsin, Wisconsin Natural Resources Foundation, USDA Wildlife Services, Sand Valley Restoration LLC, Meteor Timber, the Wisconsin Trapshooting Association, Bayfield, Marinette, Vilas, and Jackson County Forest Departments, and many birders and other private citizens.

An article is planned for the June edition of Wisconsin's Natural Resources magazine that will highlight Wisconsin's efforts to conserve Kirtland's Warbler over the last 10 years.